The invention relates to a light signal transmitter for an optical sensor and to a light receiver
Optical sensors are used in many non-industrial and primarily also industrial applications, in particular in industrial automation arrangements, in a wide variety of designs for detecting the presence or absence of objects or persons. Known exemplary embodiments are light barriers or light probes, in which a light beam is emitted by a light signal transmitter, that is to say a light source, and is received by a photocell, a light-sensitive semiconductor component or a similar sensor element; in this case, the term light probe denotes “reflected light barriers” in which light source and receiver (sensor) are integrated with one another in a single device.
In order to construct a system which is as robust and independent of stray light as possible and which can monitor even relatively large distances (detection ranges), beam shaping of the light has to be effected at the light signal transmitter (transmitter). For this purpose, the actual light source (LED; semiconductor laser diode) is regularly provided with an optical assembly, for example with a lens or a lens system (“objective”). A comparatively small light spot is thus generated which ensures high switching and repeat accuracy upon the entry of objects into the light beam and reduces mutual influencing of systems of identical type installed alongside one another (that is to say improves the signal-to-noise ratio), and the possible detection distance (distance) is increased. Such a constructional embodiment of the light signal transmitter, by virtue of the optical assembly disposed upstream, gives rise to arrangements having comparatively large dimensions or else arrangements having housings from which the optical assemblies project. In the case of confined space conditions, however, flat housing dimensions are demanded, which cannot be realized by the known arrangements. The dimensions of known light receivers (light detectors, “optical receivers”) which receive the light emitted by the light signal transmitters of the optical sensors are likewise disadvantageous, since they, too, cannot be constructed in an arbitrarily flat fashion by virtue of optical assemblies disposed upstream.